Structure and properties of non-classical polymers Part XIII. 1-D high-spin polymers with out of chain radical sites

Abstract

The magnetic properties of some classes of 1-D high-spin alternant organic polymers were studied theoretically. The objects considered in this paper are π-conjugated linear polymers bearing radical groups that are attached to the π-conjugated backbone to yield non-classical (non-Kekule) structures (pendant-type polyradicals). The polymers have similar energy spectra: a large energy gap in the middle of which a half-filled band (HFB) of degenerate MOs is situated. In all cases the π-electrons within the HFB are ferromagnetically coupled with the main contribution of the direct (Coulomb) exchange. However, the different topologies and geometries of the polymers determine the essentially different magnitude of the magnetic coupling. Especially the high-spin derivatives of polymers built up from poly(acene) cata-condensed chains (ribbons) are characterized by very large values of the effective exchange integral which increases drastically with increasing the number of the poly(acene) ribbons.